Revert of Remove InputMethodEventHandler.

ash/host/ash_window_tree_host_x11.h

Index: ash/host/ash_window_tree_host_x11.h
diff --git a/ash/host/ash_window_tree_host_x11.h b/ash/host/ash_window_tree_host_x11.h
index 6cf37a7273a0ee2a94aefd1e300e7fcad3352ca2..6389c07f2081b35c1d121fd6c7e562eaea01961f 100644
--- a/ash/host/ash_window_tree_host_x11.h
+++ b/ash/host/ash_window_tree_host_x11.h
@@ -53,6 +53,10 @@
   void OnWindowInitialized(aura::Window* window) override;
   void OnHostInitialized(aura::WindowTreeHost* host) override;
 
+  // ui::internal::InputMethodDelegate:
+  ui::EventDispatchDetails DispatchKeyEventPostIME(
+      ui::KeyEvent* event) override;
+
   // Set the CrOS touchpad "tap paused" property. It is used to temporarily
   // turn off the Tap-to-click feature when the mouse pointer is invisible.
   void SetCrOSTapPaused(bool state);